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Diffstat (limited to '')
| -rw-r--r-- | crypto/jitterentropy-kcapi.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c new file mode 100644 index 000000000..e8a4165a1 --- /dev/null +++ b/crypto/jitterentropy-kcapi.c @@ -0,0 +1,223 @@ +/* + * Non-physical true random number generator based on timing jitter -- + * Linux Kernel Crypto API specific code + * + * Copyright Stephan Mueller <smueller@chronox.de>, 2015 + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, and the entire permission notice in its entirety, + * including the disclaimer of warranties. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of the author may not be used to endorse or promote + * products derived from this software without specific prior + * written permission. + * + * ALTERNATIVELY, this product may be distributed under the terms of + * the GNU General Public License, in which case the provisions of the GPL2 are + * required INSTEAD OF the above restrictions. (This clause is + * necessary due to a potential bad interaction between the GPL and + * the restrictions contained in a BSD-style copyright.) + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF + * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT + * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR + * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE + * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH + * DAMAGE. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/fips.h> +#include <linux/time.h> +#include <crypto/internal/rng.h> + +#include "jitterentropy.h" + +/*************************************************************************** + * Helper function + ***************************************************************************/ + +void *jent_zalloc(unsigned int len) +{ + return kzalloc(len, GFP_KERNEL); +} + +void jent_zfree(void *ptr) +{ + kfree_sensitive(ptr); +} + +int jent_fips_enabled(void) +{ + return fips_enabled; +} + +void jent_panic(char *s) +{ + panic("%s", s); +} + +void jent_memcpy(void *dest, const void *src, unsigned int n) +{ + memcpy(dest, src, n); +} + +/* + * Obtain a high-resolution time stamp value. The time stamp is used to measure + * the execution time of a given code path and its variations. Hence, the time + * stamp must have a sufficiently high resolution. + * + * Note, if the function returns zero because a given architecture does not + * implement a high-resolution time stamp, the RNG code's runtime test + * will detect it and will not produce output. + */ +void jent_get_nstime(__u64 *out) +{ + __u64 tmp = 0; + + tmp = random_get_entropy(); + + /* + * If random_get_entropy does not return a value, i.e. it is not + * implemented for a given architecture, use a clock source. + * hoping that there are timers we can work with. + */ + if (tmp == 0) + tmp = ktime_get_ns(); + + *out = tmp; +} + +/*************************************************************************** + * Kernel crypto API interface + ***************************************************************************/ + +struct jitterentropy { + spinlock_t jent_lock; + struct rand_data *entropy_collector; + unsigned int reset_cnt; +}; + +static int jent_kcapi_init(struct crypto_tfm *tfm) +{ + struct jitterentropy *rng = crypto_tfm_ctx(tfm); + int ret = 0; + + rng->entropy_collector = jent_entropy_collector_alloc(1, 0); + if (!rng->entropy_collector) + ret = -ENOMEM; + + spin_lock_init(&rng->jent_lock); + return ret; +} + +static void jent_kcapi_cleanup(struct crypto_tfm *tfm) +{ + struct jitterentropy *rng = crypto_tfm_ctx(tfm); + + spin_lock(&rng->jent_lock); + if (rng->entropy_collector) + jent_entropy_collector_free(rng->entropy_collector); + rng->entropy_collector = NULL; + spin_unlock(&rng->jent_lock); +} + +static int jent_kcapi_random(struct crypto_rng *tfm, + const u8 *src, unsigned int slen, + u8 *rdata, unsigned int dlen) +{ + struct jitterentropy *rng = crypto_rng_ctx(tfm); + int ret = 0; + + spin_lock(&rng->jent_lock); + + /* Return a permanent error in case we had too many resets in a row. */ + if (rng->reset_cnt > (1<<10)) { + ret = -EFAULT; + goto out; + } + + ret = jent_read_entropy(rng->entropy_collector, rdata, dlen); + + /* Reset RNG in case of health failures */ + if (ret < -1) { + pr_warn_ratelimited("Reset Jitter RNG due to health test failure: %s failure\n", + (ret == -2) ? "Repetition Count Test" : + "Adaptive Proportion Test"); + + rng->reset_cnt++; + + ret = -EAGAIN; + } else { + rng->reset_cnt = 0; + + /* Convert the Jitter RNG error into a usable error code */ + if (ret == -1) + ret = -EINVAL; + } + +out: + spin_unlock(&rng->jent_lock); + + return ret; +} + +static int jent_kcapi_reset(struct crypto_rng *tfm, + const u8 *seed, unsigned int slen) +{ + return 0; +} + +static struct rng_alg jent_alg = { + .generate = jent_kcapi_random, + .seed = jent_kcapi_reset, + .seedsize = 0, + .base = { + .cra_name = "jitterentropy_rng", + .cra_driver_name = "jitterentropy_rng", + .cra_priority = 100, + .cra_ctxsize = sizeof(struct jitterentropy), + .cra_module = THIS_MODULE, + .cra_init = jent_kcapi_init, + .cra_exit = jent_kcapi_cleanup, + + } +}; + +static int __init jent_mod_init(void) +{ + int ret = 0; + + ret = jent_entropy_init(); + if (ret) { + pr_info("jitterentropy: Initialization failed with host not compliant with requirements: %d\n", ret); + return -EFAULT; + } + return crypto_register_rng(&jent_alg); +} + +static void __exit jent_mod_exit(void) +{ + crypto_unregister_rng(&jent_alg); +} + +module_init(jent_mod_init); +module_exit(jent_mod_exit); + +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); +MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter"); +MODULE_ALIAS_CRYPTO("jitterentropy_rng"); |